MCAT Demo Test Biology Section Questions and Answers

MCAT Demo Test Biology Section Questions and Answers The stability of the collagen triple helix depends partly on the repetitive sequence of amino acids which comprise the individual alpha helices. Which of the following amino acids most likely faces the center of the collagen triple helix? - Correct Answer️️ - Glycine The most stable structure for the collagen triple helix will likely feature the amino acid with the least sterically-hindered functional group facing the center of the helix; as such, glycine, whose functional group is a mere hydrogen atom, will be most likely to face the center of a stable triple helix It has been shown that hydroxylation of proline in the presence of ascorbic acid dramatically increases the stability of the procollagen superstructure that comprises collagen. Which of the following likely contributes most to the added stability that results from hydroxylation? - Correct Answer️️ -Stereoelectronic effects Based on information in the passage and data presented in Figures 2 and 3, the absence of ascorbic acid causes which of the following outcomes? - Correct Answer️️ -Decrease in the rate of pro-collagen secretion. Once radiolabeled for detection, which of the following amino acids would be LEAST likely to accurately measure the amount of non-procollagen secreted? - Correct Answer️️ -Hydroxyproline Hydroxyproline is considered a non-proteinogenic - or, "unnatural" - amino acid in the sense that it is not typically found in the proteins that comprise the body. In addition to its absence in the list of twenty-one proteinogenic amino acids (the usual 20 plus selenocysteine), it may be inferred from the passage that hydroxyproline is created specifically for the increased stability of collagen. Which of the following is an example of horizontal gene transfer? - Correct Answer️️ - Conjugation between an Hfr and an F- bacterium. According to the passage, horizontal gene transfer is a process in which an organism incorporates genetic material from another organism without being the offspring of that organism. Conjugation, the passing of genetic material from bacteria to bacteria via a conjugation bridge, is an example of this. The fact that the Sputnik genome contains both mimivirus and mamavirus genes supports the conclusion that it participates in a process similar to: - Correct Answer️️ - Transduction The Sputnik genome containing genes from its mamavirus host is similar to a bacteriophage viral genome that contains bacterial host genes, as happens in transduction Which of the following is a viral agent that could be used in the development of phage therapy? - Correct Answer️️ -T4-like coliphages Phage therapy is the use of bacteriophage to treat bacterial infections. As described in the passage, the theory is that the virus will attack the disease-causing bacteria and not the human host. Phage therapy would be a more effective treatment option than antibiotics in each of the following EXCEPT: - Correct Answer️️ -Meningitis caused by Staphylococcus aureus that are sensitive to the drug oxacillin. Phage Therapy would be effective for the following: Steomyelitis, a bone infection where circulation at the infection site is poor. Chronic urinary tract infection caused by a biofilm, a complex mixture of microbes that resist the effects of antibiotics. Pneumonia caused by penicillin-resistant Streptococcus pneumoniae. Which of the following is true regarding action potentials in cardiac cells? - Correct Answer️️ -Repolarization in both the pacemaker cells and myocytes is due to the efflux of potassium. One analytical tool for determining the amount of iron in blood is to treat the blood with cyanide ion, which complexes with the Fe2+ in hemoglobin and displaces the porphyrin to form the hexacyanoferrate(II) complex ion, [Fe(CN)6]4-. Which of the following statements supports the use of this method as a quantitative way of determining the iron concentration? - Correct Answer️️ -The formation constant (Kf) of the [Fe(CN)6]4- ion is much larger than that of the Fe2+-hemoglobin complex. A scientist has a vial of cells that can be grown on plates in the lab. She does a transformation experiment on these cells and isolates the RNA a few days later. Which of the following is true about the cells under study? - Correct Answer️️ -To extract the RNA, the researcher would have to break down the cell wall and the plasma membrane. Which of the following is true regarding the function of the right and left ventricles? - Correct Answer️️ -The right ventricle and left ventricle produce unequal systolic pressures, but have equal ejection fractions. The right ventricle only supplies the pulmonary circulation and would not require, nor have the ability, to produce the pressure needed to supply the systemic circulation, as the left ventricle does. A researcher studying the visual cortex attempts to record visually evoked responses from a single neuron but is not observing any change in the firing rate of action potentials when the stimulus is presented, regardless of how bright it is. What is the most likely reason for this observation? - Correct Answer️️ -The orientation of the stimulus is not ideal. The passage explains that sensory neurons display differing responses depending upon the stimulus. If the cell being recorded from responds to a light stimulus in one orientation, but not the other, this could explain the lack of a response An individual action potential in a model neuron results in 100 sodium ions crossing the cell membrane. Given that the sodium-potassium pump requires a single molecule of ATP per cycle, how many acetyl-CoA would be required to generate enough energy to extrude the new sodium in the cell via the pump? - Correct Answer️